#### Answer

3$\sqrt 3$

#### Work Step by Step

You are given $\sqrt 3$+$\sqrt {12}$.Simplify $\sqrt {12}$ to get 2$\sqrt 3$. You have $\sqrt 3$+2$\sqrt 3$ and can now simplify it:
1$\sqrt 3$ +2$\sqrt 3$ -use distributive property to simplify similar elements-
$\sqrt 3$(1+2) -simplify-
=3$\sqrt 3$